The union flag flies at Belfast city hall on 19 February to mark the birthday of Prince Andrew. Photograph: Sean Harkin/Demotix/Corbis

Two leaders of the loyalist protests against Belfast city council's decison to restrict flying the union flag have been arrested.

It is understood that Jamie Bryson and Willie Frazer will be questioned on suspicion of organising and participating in unlawful parades.

About 150 people have been arrested and charged with offences connected to the street disorder since December.

While the majority of demonstrations across Northern Ireland have been peaceful, a number of protests turned violent, with attacks on police and members of the centrist Alliance party.

The loyalists targeted Alliance because it holds the balance of power at Belfast city hall, and it was Alliance votes at a council meeting on 3 December that changed the flag-flying policy from 365 days a year to a designated 18.

Frazer, who is a prominent campaigner for unionist victims of the Troubles, was arrested in his home village of Markethill, County Armagh.

With Bryson, the 52-year-old has been one of the leading voices of the flag protests over the past 11 weekends.

Earlier this week, the Police Service of Northern Ireland's chief constable, Matt Baggott, suggested the laws surrounding unnotified parades may need to be reviewed so as to provide more of a deterrent against illegal demonstrations.

"I remain concerned that the current Public Processions Act does not provide sufficient deterrence to those breaking the law," he said.

"The required standard of proof to convict is high, and the Act would benefit from review."